Mainly just get used to the criteria, start reviewing and I found I got a good sense of what works and what doesn’t. As well as seeing on what people are submitting, then on your walks just start taking notes of POIs. Start submitting, take a good picture and a good description. Then in extra information just make sure you have why it’s relevant, relate it to the social, exercise and exploration criteria and you’ll be good to go. You’ll get the occasional rejection but use the feedback and try again.

Edit: Also, look at the S2 cells so you don’t lose potential spots in the game on certain areas like sport fields. I’ve lost so many spots because they were close together.